Two critical factors in the flight of any aircraft or airplane are the weight and balance of that aircraft or airplane. An airplane manufacturer must determine and publish the maximum operating weight of that airplane. This is to insure that at take-off speed, the wings are generating sufficient lift to lift the weight of the airplane. A second but equally important factor to consider is whether the airplane is in balance (optimum location for the center of gravity) or within acceptable limits, as can be compensated for by trim adjustments. Calculations to determine weight and center of gravity in terms of percent MAC (Mean Aerodynamic Chord) are well known and well documented. Reference may be made to U.S. Pat. No. 3,513,300 to Elfenbein.
Prior art methods to determine weight and center of gravity are performed using measurements of some portions of the aircraft's payload and estimates of the remaining portions of the aircraft's payload. This information is input into ground computers which calculate weight and center of gravity. The calculations are relayed to the pilot in the aircraft before take-off.
This invention relates to improvements to the previous so-called "Weight and Center of Gravity Indicators". The lack of those systems being utilized by the major air carriers, reinforces the position that those systems are not accurate nor reliable on today's modern aircraft landing gear. Today's aircraft landing gear struts incorporate the shock absorbing technique of forcing hydraulic fluid through a small orifice hole within the strut cylinder. Compressed nitrogen gas is used to retard foaming of the hydraulic fluid as it passes through this orifice. Multiple O-ring seals and a gland nut around the piston are used to retain the hydraulic fluid and compressed nitrogen gas contained within each strut cylinder. The retention of the compressed nitrogen gas and hydraulic fluid by the O-ring seals is due to the extreme amount of friction these seals maintain as they move up and down the interior strut cylinder walls. This friction causes substantial drag to this up and down movement. While this may improve the shock absorbing quality of the strut, IT DISTORTS INTERNAL PRESSURES WITHIN THE LANDING GEAR STRUT AS THOSE PRESSURES RELATE TO THE AMOUNT OF WEIGHT THE STRUT IS SUPPORTING.
In the present invention, temperature, drag and hysteresis compensation values are used to correct for the distorted pressure readings caused by drag within the landing gear struts. This produces more accurate weight and center-of-gravity measurements of an aircraft.
The airline industry may not wish to give up the methods for estimating weights, that they have been using for years. This new system could then complement their current practices by giving the pilots a verification, of data received from the ground computers, that one or more of the input figures to the ground computer, were not entered in error or possibly that some numbers have not been transposed. The decision whether or not to attempt a take-off, ultimately is made by the pilot in command. This new system will give more accurate information, which can be used to make that decision.
Fuel costs are a major concern to the airline industry. Frequently airplanes are held at the gate prior to departure, waiting for estimated weight and center of gravity calculations to be determined and transmitted from the ground computers to the pilots. Often those figures are delayed or if they come back beyond the airplanes limits, adjustments must be made at the gate. This new system progressively calculates those figures as the airplane is being loaded, giving those total figures to the pilots as the airplane doors are being closed. These real time weight and center-of-gravity measurements would allow the airplane to immediately leave the gate, thus saving fuel industry wide.
Cost effectiveness is another major concern of the airline companies; getting the most revenue from each flight that an airplane makes. With the current system of estimating weight, the airline companies must factor in margins for error in their calculations, which can result in unnecessary empty seats or less cargo transported. This new system, which more accurately determines the airplane weight, could reduce those margin amounts and allow more income producing cargo to be transported on each flight.
Still another application of this new system could be the general aviation industry (the private and corporate pilots). These pilots do not have the sophisticated weight and balance computers, used by the airline companies, at their disposal. These pilots must weigh each and every item loaded on to their airplanes, or as many pilots do, just estimate or guess at it. This new system will provide for these pilots the same benefits as discussed for the airline pilots.